冬季组合工艺处理灌溉尾水的运行效果

采用水耕蔬菜人工湿地与垂直流人工湿地组合工艺处理农村生活污水灌溉尾水,针对冬季灌溉尾水量大,而系统处理效果下降问题,对组合工艺进行了运行效果及水力负荷等工艺参数的优化研究。大棚对系统能起到一定的保温效果,系统进出水水温均高出未采取保温强化措施系统2℃左右。在冬季水耕蔬菜人工湿地与垂直流人工湿地受温度影响,污染物去除效能显著下降,随着水力负荷的增大,水耕蔬菜人工湿地对COD、TN及TP的平均去除率和去除负荷呈先增加后减小趋势,其对COD、TP的平均去除率均在0.3 m3/(m2·d)附近达到最大,分别为33.4%和11.5%,TN的平均去除率在0.4 m3/(m2·d)附近达到最大,为8.5%;垂直流人工湿地随着水力负荷的增大,对COD、TN、NH4+-N和TP的平均去除率的变化趋势与水耕蔬菜人工湿地相似,在0.2 m3/(m2·d)处达到最大,分别为56.3%、29.3%、23.8%和31.3%。上述结果与人工湿地在其他温度较高季节去除率一般随水力负荷降低而呈上升趋势的结果显著不同,表明在冬季依靠一味降低水力负荷无法达到提高系统去除效能的目的。

Operating effect of combined process treating irrigation tail water in winter

A combined process involving an aquatic vegetation constructed wetland (AVCW) and a vertical flow constructed wetland (VFCW) was used to treat irrigation tail water produced from rural domestic sewage. The treatment efficiency of the system declined when irrigation tail water increased in winter. Hence, the operating efficiency was investigated and hydraulic loading was optimized in winter. Data showed that a greenhouse could provide a certain heat preservation function for the system, and water temperature of the system with a greenhouse was about 2℃ higher than that for a system without a greenhouse. Contaminant removal efficiency of the AVCW and VFCW declined significantly in winter owing to the low temperatures. The average removal rates of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorous (TP) for the AVCW showed a decreasing trend after first increasing when the hydraulic loading rate increased. The average removal rates of COD and TP were 33.4% and 11.5%, respectively, and the values reached their maximum near 0.3 m3/(m2·d), while the average removal rate of TN was 8.5%, and it reached its maximum near 0.4 m3/(m2·d). The average removal rates of COD, TN, NH4+-N, and TP for the VFCW showed trends similar to those for the AVCW when hydraulic loading rates increased. The average removal rates of COD, TN, NH4+-N, and TP were 56.3%, 29.3%, 23.8%, and 31.3%, respectively, and the values reached their maximum near 0.2 m3/(m2·d). In the warm season, the removal rate of an artificial wetland generally rises with reduced hydraulic loads, and the results presented here are obviously different from warm season trends. In general, the results showed that the removal efficiency of the system cannot be enhanced only by reducing hydraulic loading in winter.